Secure and reliable document delivery using routing lists

ABSTRACT

An operations center (OC) ( 200 ) acts as an intermediary for securely and reliably transmitting a document ( 3 ) from a sender ( 100 ) to a next recipient ( 300 ) on a routing list. The OC ( 200 ) identifies ( 464 ) a recipient ( 300 ) from the next stage of the routing list and provides either the recipient&#39;s public key ( 404 ) or an escrow encryption key ( 406 ). The OC ( 200 ) optionally can authenticate the sender ( 100 ) and/or the recipient ( 300 ), thus increasing security.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(e) to U.S.Provisional Patent Application Ser. No. 60/242,013, “Efficient Methodfor Routing Deliveries through Recipient Translation,” by Eng-Whatt Toh,filed 19 Oct. 2000.

This application is a continuation-in-part of commonly assigned U.S.patent application Ser. No. 09/887,157, “Secure and Reliable DocumentDelivery,” by Eng-Whatt Toh, et al., filed Jun. 21, 2001; which claimspriority under 35 U.S.C. § 119(e) to U.S. Provisional Patent ApplicationSer. No. 60/216,734, “A VPN-Based Digital Delivery System,” by Eng-WhattToh, filed 7 Jul. 2000, U.S. Provisional Patent Application Ser. No.60/242,015, “Application VPN with Application Proxies,” by Eng-WhattToh, filed 19 Oct. 2000; and U.S. Provisional Application Ser. No.60/242,014, “Method For Fast Escrow Delivery,” by Chee-Hong Wong,Kok-Hoon Teo, See-Wai Yip, and Eng-Whatt Toh, filed 19 Oct. 2000.

The subject matter of all of the foregoing is incorporated herein byreference in their entirety.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates generally to secure and reliable transmission ofdata. More particularly, the invention relates to computer-implementedtechniques for securely and reliably transmitting an electronic documentalong a routing list using a secure, central key managing intermediary.

2. Background Art

With the advent of computers and the Internet, an increasing number ofdocuments is being transmitted in electronic format between anincreasing number of recipients, and there is a growing acceptance ofthe electronic delivery of documents. For example, many companiestransact business through the use of documents, such as contracts,memos, emails, etc. In order to transact business, these documents oftenare circulated for approval or review. As a result, it is becomingincreasingly important to be able to deliver these documents in a secureand reliable manner. It is also becoming increasingly important for thedelivery service to be flexible in order to handle more complexdistribution and routing lists.

While unsecured email is perhaps one of the most common electronicdelivery methods, it typically is not secure, flexible or particularlyreliable. Other approaches to electronic delivery exist which are moresuccessful in attempting to provide either secure or reliable deliveryof documents. Two of the more common approaches are secure electronicmail (a.k.a., secure email) and Secure Socket Layer (“SSL”) baseddeliveries using a Web site for uploading and downloading of deliveries.However, neither of these delivery methods is fully satisfactory withrespect to security or reliability and generally is no better thanunsecured email with respect to flexibility.

Secure email is similar to unsecured email, except that email messagesare secured using encryption. In unsecured email, the sender transmitshis message to the recipient in an unencrypted state. Thus, if a thirdparty intercepts the message en route to the recipient, the third partywill be able to read the message. In secure email, the sender firstencrypts the message using a key and then transmits the encryptedmessage to the recipient. If a third party intercepts this message, itwill be unintelligible to the third party since he presumably does nothave enough information to decrypt the message (e.g., the third partynormally does not have the correct key required to decrypt the message).The recipient, on the other hand, does have the information required todecrypt the message and therefore can read the message when he receivesit. By limiting access to the decryption method and keys, the sender canlimit who is able to read an encrypted message. By encrypting themessage before transmitting, the message is protected duringtransmission.

However, secure email is delivered from the sender to the recipientusing the same architecture and infrastructure as unsecured email and,therefore, suffers from many of the same drawbacks as unsecured email.For example, secure email delivery services generally lack reliabilitydue to the architecture of the email delivery system and are limited tothe same types of distribution as unsecured email. Conventional emailservers are designed upon a store-and-forward architecture. An emailmessage may be routed through several email servers on its way from thesender to the recipient, with each server receiving the incomingmessage, determining the next server on the message's journey,transmitting the message, and possibly leaving behind a copy causingunnecessary and unmanageable audit trails. No single machine isresponsible for ensuring that the entire message has been successfullytransmitted from the sender to the recipient. In addition, each of theemail servers in the chain from sender to recipient is usually owned andoperated by a different party. Since no single company or entity ownsthe entire delivery chain for the email message, no one company orentity can guarantee reliable delivery or integrity of the message. Thestoring-and-forwarding of email documents through several servers ownedby multiple parties means that email messages get lost, delayed, andcorrupted. This makes the overall delivery service unreliable oruntrackable, and this is just in the context of a delivery from onesender to one recipient. These problems are aggravated if the documentis to be routed among multiple recipients, for example along a routinglist over the Internet. Encrypting an email message may provide someprotection against unwanted disclosure during transit, but it does notaddress the reliability issue, does not guarantee that the message willbe delivered to the recipient, and does not provide the flexibility tosupport more sophisticated routing lists with end to end tracking.

An alternate approach to document delivery services utilizes the SecureSocket Layer Protocol for security. In this approach, a Web site usesits digital certificate to authenticate itself to the sender using theSSL protocol. Once the Web site is authenticated, a secure channel isset up between the sender's browser and the Web site, typically bygenerating a session key to encrypt transmissions between the two. Thedocument is sent from the sender's browser to the Web site via thesecure channel. It is stored at the Web site, typically in unencryptedform, awaiting delivery to the recipient. During delivery, the Web siteauthenticates itself to the recipient's browser and a securecommunications channel is then set up between the Web site and therecipient's browser. The document is delivered to the recipient via thesecure channel.

The SSL approach suffers from many drawbacks. For example, although theWeb site authenticates itself using its digital certificate, neither thesender nor the recipient authenticates himself using a digitalcertificate. Typically, these systems would at most require the senderand the recipient to authenticate themselves using passwords, which isweak security. In other words, there is no real assurance that eitherthe sender or the recipient actually is who he claims to be. As aresult, there is also a lack of non-repudiation, meaning that at a latertime, the sender can plausibly deny having sent the document simply bypointing out that there is no strong evidence of who actually sent thedocument.

Another drawback is that these systems lack end-to-end security, becauseSSL secures only the channels. The document typically remains inunencrypted form while it is temporarily stored at the Web site. Hence,a third party which attacks the Web site and gains access to thedocument will be able to read the document. In addition, if the Web siteis untrustworthy (or happens to hire an untrustworthy employee), thedocument will be vulnerable.

There are also SSL-based services that provide optional passwordencryption of the documents. These systems provide better security,since the document is encrypted at the point of transmission. However,these systems are difficult to use since they require the sender tocommunicate the password out-of-band to the recipient, a process that iscumbersome and fraught with security risks. Such a system also does notguarantee non-repudiation, since it neither strongly authenticates auser, nor supports digital signatures, nor ensures that only therecipient could open a delivery.

There are also SSL-based services that provide optional encryption ofthe documents using certificates. These systems provide end-to-endcontent security, but are extremely difficult to use because of the needfor users to manually obtain the keys and exchange keys prior toencryption. Unfortunately, these systems do not integrate key managementwith encryption and reliable delivery, leaving the complexity of keymanagement entirely to the user. In addition, a system that requiresoptional use of certificates cannot guarantee non-repudiation. Theabsence of a digital signature does not represent the absence of atransaction, because the sender could have opted to not use acertificate. Absolute non-repudiation requires mandatory and uniform useof certificates for all transactions in a system.

Finally, the SSL approach, like secure email delivery services, istypically focused on delivering documents from one sender to onerecipient(s). As a result, more complex deliveries, such as those usingrouting lists, can be difficult to implement. For routing lists to beeffectively implemented, deliveries should be tracked end to end. Inthis way, the progress of a delivery along the routing list can betracked and the delivery can be correctly routed to the nextrecipient(s). Secure email services typically cannot implement end toend tracking for the reasons discussed above. In addition, to facilitatebusiness-to-business routing of documents over a public network such asthe Internet, strong security is often a requirement. SSL servicestypically cannot provide strong security. Neither the SSL approach northe secure e-mail approach currently provides sufficient security andreliability to facilitate a robust implementation of routing lists overpublic networks.

In contrast, existing workflow systems can facilitate the routing ofdocuments between various recipients but they typically are limited tointernal communications and cannot be used securely or reliably tocommunicate with the outside world. Typically, a workflow server storesa document online and decides who should get the document next andnotifies the next recipient to come and get it. One example of such aworkflow system is Lotus Notes, in which documents and forms aredatabase driven and the next recipient is notified once certain priorconditions, as determined by a central server, are met. These systemstypically require that all of the recipients have access to a commondatabase or common software. However, companies are reluctant to storetheir documents in databases which are widely accessible from theoutside due to security concerns. Alternatively, the routing rules canbe embedded as part of the delivery but proprietary software is requiredto decipher and execute the embedded rules. This approach is notsuitable for use between different companies because companies typicallyare not willing to install common software just to facilitate workflowwith one of its business partners. Thus, in practice, current workflowsystems are confined to well-defined, closed communities.

Therefore, there is a need for a flexible delivery system which providesintegrated key management so that reliable delivery and end-to-endsecurity can be achieved, thus providing some or all of the followingbenefits: (1) reliable/guaranteed delivery for transactions—a deliverywill not be lost; (2) confidentiality for transactions—only therecipient can open a delivery; (3) non-repudiation for transactions; and(4) complex routing of transactions among multiple recipients, includingover the Internet between different organizations.

DISCLOSURE OF INVENTION

A computer-implemented method, system, and computer-readable medium forsecurely and reliably transmitting a document (3) from a sender (100) toa next recipient (300) on a routing list using a central operationscenter (“OC”) (200). The OC (200) receives (462) an indication that thesender (100) desires to deliver the document (3) to a next stage on arouting list for the document. The OC (200) identifies (464) a recipient(300) from the next stage of the routing list and provides a key, eitherthe recipient's public key (404) or an escrow encryption key (406). TheOC (200) optionally can authenticate the sender (100) and/or therecipient (300) using their respective public keys, thus increasingsecurity.

In one implementation, the key (404,406) is transmitted (485) to thesender (100). For example, if the key is the recipient's public key(404), it may be transmitted in the form of a digital certificate. Thesender (100) encrypts (490) the document (3) using the key (404,406) andtransmits the encrypted document to the recipient (300), either directly(630) or indirectly (530) via the OC (200). In an alternate embodiment,the OC (200) encrypts the document using the key (404,406).

The routing list may also be implemented in many ways. In oneimplementation, the routing list is identified by a special emailaddress or domain name. Documents which are delivered to the emailaddress or domain name are interpreted as using a routing list. Inanother variation, the routing list includes rules, for example ruleswhich implement a business process or which determine who the nextrecipient is. In these cases, some of the recipients may be conditionalrecipients, meaning that they will be on the routing list only ifcertain conditions are met.

In one implementation, the OC (200) tracks the current recipient of therouting list. The tracking is updated as the document is routed todifferent recipients. For example, the OC (200) may wait forconfirmation that the next recipient on the routing list has receivedthe document before updating its tracking.

One advantage of using a central OC (200) is that secure, reliabledelivery of documents can be made in a more efficient manner. Forexample, the OC (200) can form secure, reliable connections with boththe sender (100) and the recipient (300), thus effectively generating acommunications channel from the sender (100) to the recipient (300) butwithout requiring that each possible sender (100) connect to eachpossible recipient (300). The use of routing lists supports more complexdistribution paths for a document, and the central OC (200) canefficiently track the document as it is routed along the routing list.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other more detailed and specific objects and features of thepresent invention are more fully disclosed in the followingspecification, reference being had to the accompanying drawings, inwhich:

FIG. 1 is a schematic representation of a sender (100) delivering adocument to a next recipient (300) on a routing list via a single-nodeOperations Center (200);

FIG. 2 is a schematic representation of a sender (100) delivering adocument to a next recipient (300) on a routing list via a multiple-nodeOperations Centers (200);

FIG. 3 is a functional block diagram of a preferred embodiment of thesystem shown in FIG. 1;

FIG. 4 is a flow diagram illustrating operation of the systems in FIGS.1-3;

FIG. 5 is a flow diagram illustrating operation of the systems in FIGS.1-3 in which the delivery (510) is sent via the OC (200);

FIG. 6 is a flow diagram illustrating operation of the systems in FIGS.1-3 and 9, in which the sender (100) and the recipient (300) establish adirect and secure connection (2C) between them;

FIG. 7 is a flow diagram illustrating operation of the systems in FIGS.1-3 and 9, in which the sender (100) and the recipient (300) establish adirect and secure connection (2C) between them;

FIG. 8 is a flow diagram illustrating the registration of a client (899)with the OC (200);

FIG. 9 is a schematic representation of a sender (100) transmitting adelivery (510) to a recipient (300) by transmitting at least a portionof the delivery (500) via an OC (200) and the remainder of the delivery(505) via a secure connection (2C) with the recipient (300);

FIGS. 10A-10C are tables illustrating examples of routing lists.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before turning to the Figures, it is instructive to review someprinciples of cryptography. Cryptographic algorithms can generally bedivided into two classes: symmetric key cryptography and asymmetric keycryptography. The keys themselves are typically large numbers derivedfrom complex mathematical algorithms. These keys are used to encryptand/or decrypt a message.

Symmetric key cryptography uses a single key to both encrypt and decrypta message. A message encrypted with a symmetric key can, for allpractical purposes, be decrypted only by that same key. For example, ifa sender encrypts a message with a symmetric key and sends the encryptedmessage to a recipient, the recipient can decrypt the message only if hepossesses the same key that the sender used to encrypt the message. Oneof the benefits of using symmetric keys is efficiency. The amount ofcomputing (and therefore, the amount of time) necessary for encryptingand decrypting the message is less than that required for otherencryption methods. Thus, the delay experienced by the sender andrecipient during the encryption and decryption processes may beminimized.

Asymmetric key encryption, also called public-key encryption, involves apair of keys—a public key and a private key. Once a user has generated akey pair, the user typically keeps the private key secret but publishesthe corresponding public key. The public key and the private key aremathematically related so that one key can decrypt a message encryptedby the other key. However, the mathematical relationship between thekeys is sufficiently complex that it is computationally infeasible toderive one key given the other. Thus, if a sender wants to send amessage to a recipient in a manner such that only the recipient can readthe message, the sender can encrypt the message with the recipient'spublic key. Since only the recipient's private key can decrypt themessage, the sender can be assured that only the recipient can read themessage, assuming that the recipient is the only one with access to hisprivate key.

In addition to encrypting messages so that only specific individuals candecrypt the messages, public-key encryption can also be used for otherimportant purposes. For example, public-key encryption allows therecipient of a document to verify the identity of the sender. Assumingthat a document is encrypted using the sender's private key, it can bedecrypted only by the corresponding public key. Thus, if a recipient candecrypt a document using a certain person's public key, he can beassured that the document was originally encrypted using thecorresponding private key. Thus, the recipient can be assured that thecertain person was the one sending the document. In other words, thedocument has been digitally signed by the sender.

However, for this identification to be effective, the recipient mustreceive the sender's public key in a manner in which the recipienttrusts that the key is in fact the sender's public key and not someoneelse's public key. This trusted transmission of the sender's public keycan occur in several ways. For example, the sender could personally givethe public key to the recipient. Alternatively, the sender could deliverthe public key via a trusted delivery service.

Another possible method is to link the sender to his public key by adigital certificate issued by a trusted third party. A digitalcertificate is a document that identifies a certain public key asbelonging to a certain entity, such as individuals, legal entities, Webservers, and the like, in a trustworthy manner. A trusted third party,known as a certificate authority or CA, typically issues a digitalcertificate. The CA issues a certificate that identifies, among otherthings, an entity and that entity's public key. In this manner, the CAacts like a notary, attesting that a certain key belongs to a certainentity. A recipient who trusts the CA can be assured that any messagedecrypted with that public key must have been encrypted with thecorresponding private key, and if only the sender has access to thatprivate key, the recipient knows that the sender sent the message.

Turning now to the Figures, FIGS. 1 and 2 are schematic representationsof systems according to the invention. The systems include a sender 100,Operations Center (“OC”) 200 and a recipient 300. The sender 100 wishesto deliver a document, which can be any type of data or electronic file,in a secure and reliable manner to the next recipient 300 on a routinglist for the document. The sender 100 may or may not know the actualidentity of recipient 300. In many cases, the sender 100 simply desiresto deliver the document to whomever happens to be next on the routinglist for the document. The OC 200 acts as a secure intermediary tofacilitate the delivery of the document. It will be noted that “sender”100 can usually be interchanged for “sending system” 100 and that“recipient” 300 can usually be interchanged for “receiving system” 300.Sender 100 and recipient 300 can represent individuals and entities. Itwill also be noted that there may be a one-to-one, one-to-many, andmany-to-one relationship between sender 100 and sending system 100 andbetween recipient 300 and receiving system 300.

In FIG. 1, the OC 200 includes a single node, which connects to both thesending system 100 and the receiving system 300. In FIG. 2, the OC 200includes multiple nodes 200A-C networked together by a secureinterconnection 200D. The sender 100 connects to a node (200A in thisexample), and the recipient 300 also connects to a node (200B in thisexample). As the number of senders and recipients (i.e., the clientbase) increases, multiple nodes can distribute the tasks described belowto better serve the clients. For example, senders and recipients canconnect to the node that is most convenient for them. In the multi-nodeconfiguration, each node is securely connected 200D to the others toensure the security and reliability of transmissions between the nodes.For convenience, the following explanations refer to a single-node OCbut they are equally applicable to multi-node OCs.

FIG. 3 is a functional block diagram of a preferred embodiment of thesystem shown in FIG. 1. In this embodiment, each of the sending system100 and the receiving system 300 includes an account profile 101, 301,authentication module 102, 302, secure connection module 103, 303 andencryption/decryption module 104, 304, all of which may communicate witheach other. In a preferred embodiment, each of the modules isimplemented as software, but can also be implemented as hardware and/orfirmware, and the account profile 101, 301 is stored locally. Examplesof sending and receiving systems 100, 300 include desktop computers,portables, PDAs and wireless phones and other digital devices. Thesystems 100, 300 can also include a key registration module 105, 305 forregistration of the sender 100 and the recipient 300 and for generatingnew key pairs as part of the key management performed by the OC 200.

The OC 200 includes the following modules: authentication module 202,messaging module 203, secure connection module 204, key manager module205, tracking module 208, and routing module 209. It also includes adirectory interface 201 and local storage 206. All of these componentsmay communicate with each other. In a preferred embodiment, the variousmodules and the directory interface are implemented as software, but canalso be implemented as hardware and/or firmware. For example, in oneembodiment, the directory interface 201 and routing module 209 areimplemented as software running on a separate computer from the othermodules. An example implementation of OC 200 would include serversoftware running on Windows NT and Sun Solaris systems.

The system in FIG. 3 also includes a public key directory 210 and anescrow manager 211, which is potentially accessible by each of thesending system 100, the OC 200, and the receiving system 300. The publickey directory 210 is a directory of public keys. For example, the publickey directory 210 may contain digital certificates which associatepublic keys to entities. The escrow manager 211 will be described infurther detail below.

The system in FIG. 3 generally operates according to the flow charts inFIG. 4-FIG. 8. However, more details will be given below concerningvarious aspects of the system and its operation.

Referring to FIG. 8, before a client 899, which could represent eitherthe sender 100 or the recipient 300, can transmit or receive a documentthrough the OC 200, the client 899 first registers with the OC 200. Asdescribed in more detail below, the registration process provides theclient 899 with an application, which facilitates registration byassociating a private-public key pair with the client 899 and byproviding the client 899 with the sending system 100 and/or thereceiving system 300. As shown in FIG. 3, many of the modules in thesending and receiving systems 100,300 are common and preferably areshared rather than duplicated.

An unregistered client 899 begins the registration process by contacting800 the OC 200 and obtaining 805 the relevant application. Theapplication can be implemented in software, firmware, hardware, or anycombination thereof. In one embodiment, the client 899 contacts the OC200 via a network connection to a server or Web site operated by the OC200. Once connected to a Web site operated by the OC 200, the client 899begins the registration process by selecting a “registration” or “newusers” icon or hyperlink. In alternate embodiments, the client 899 couldcontact the OC 200 by telephone, facsimile, email, or mail and requestthat the relevant application be sent to the client 899. For example,upon receiving 805 a software application, the client 899 loads thesoftware application onto a personal computer, such as an IBM®PC-compatible personal computer, or a workstation, such as thoseavailable from Sun Microsystems® of Mountain View, Calif.

In either of the above embodiments, the client 899 supplies 810registration information, such as his name and a valid email address, tothe OC 200 via a network connection. To protect the information that issupplied during this initial registration process, it is preferred thatthe connection between the OC 200 and client be secured. The connectioncan be secured by using a direct network connection or by using asecurity protocol, such as the Secure Socket Layer protocol. In oneembodiment, once the registration information has been submitted to theOC 200, the OC 200 sends a personal activation code to the client 899.For example, the personal activation code is sent in an email message tothe email address specified in the registration information. Only theindividual with access to that email address will normally receive thepersonal activation code. The activation code could be a set ofcharacters that the client 899 is required to enter at a specified Webpage located at the Web site operated by the OC 200. Alternatively, theactivation code could be a unique hyperlink, such as a Uniform ResourceLocator (“URL”), that when selected by client 899, causes the client'scomputer to connect to a unique Web page at the Web site operated by theOC 200. For added security, after the activation code has been enteredonce, or after the hyperlink has been selected once, the OC 200 nolonger accepts that activation code. Alternatively, in addition to theactivation code, the activation process may also require the client 899to provide a shared secret, something only the client 899 and the OC 200know, further increasing the level of security for the activationprocess.

In yet a different embodiment, the client 899 may have received 540(FIG. 5) notification that a delivery is pending, and the activationcode could be sent together with the notification, removing the need tosubmit a Web form to request for the activation code. This method alsoeffectively verifies the email address of the client 899.

After the client 899 has established a network connection to the OC 200and the activation code, and optionally a shared secret, has beenproperly supplied, the OC 200 continues the registration process bycreating 815 an account 851 for the client 899. To create the account,the OC 200 links the unique activation code to the client's previouslysupplied registration information. The client 899 is prompted to selectand enter an account name and password. Once the client 899 has enteredan account name and password, a private-public key pair (890,892,respectively) is generated 820. Alternatively, the client 899 may havean existing key pair which could be used instead of generating a newpair. The public key is added to the client's account information. Theaccount 851 includes the client's registration information, a registeredemail address, and a public key for the client 899, which will be usedto send and receive messages and for client authentication through theOC 200.

In one embodiment, the private-public key pair 890, 892 is generated bythe OC 200 and communicated to the client 899. In an alternateembodiment, the private-public key pair 890,892 is generated at theclient's computer. In the latter embodiment, the key generatingapplication can be part of the application received by the client 899.For example, the key generation modules 105, 305 can be included as partof the sending and receiving systems 100, 300. It is preferred that thekey pair be generated by the client 899 because it eliminates the needto transmit the client's private key 890. Because the private key 890 isnever transmitted, a third party cannot intercept it. In this case, onlythe public key 892 is transmitted to the OC 200. In either embodiment,the client's private key 890 is stored 825 on the client's computer inan account profile file 801 (such as account profile 101, 301 in FIG.3).

To provide additional security, the client's private key 890 stored inthe account profile 801 can be further encrypted. For example, theclient's password could be used to encrypt the private key. Byencrypting the private key 890 stored on the client's computer, anyonewho gains physical access to the client's computer cannot access theclient's private key 890 without first entering the correct account nameand password.

When the OC 200 obtains the client's public key, it associates theclient's public key 892 with the client's account 851, for example, bystoring the public key 892 in the client's account 851 file. The OC canalso optionally store 830 this associated information in a database ordirectory 210. Alternatively, the OC 200 can cause a digitalcertificate, which associates the client's information with the client'spublic key 892, to be created. The OC 200 could act as the certificateauthority (“CA”) creating the digital certificate; or, alternatively,the OC 200 could employ a trusted third-party CA to generate the digitalcertificate. Under either embodiment, the digital certificate can becreated as part of the registration processes and therefore istransparent to the client. The public key or digital certificate isstored 830 in a database or directory 210 and referenced when needed, asdescribed below, to authenticate the client 899 or as part of the securedocument (3) transmission process.

As described above, the client's account profile 801, which contains theclient's private key 890, is preferably generated and stored 825 on theclient's computer. Without more, the client 899 can utilize the deliveryservice from only that computer. Some clients may wish to access thedelivery service from multiple computers 997, 998, 999 (FIG. 2). In oneembodiment, to allow clients a simple method to access the deliveryservice from multiple computers 997, 998, 999, the client need only copythe account profile to the additional computers or workstations 997,998, 999. For example, the client 899 could copy the account profile 801on to a floppy disk or other computer readable medium or smart cards,and then load that account profile 801 onto any additional computer orworkstations 997, 998, 999 from which the client 899 wishes to accessthe OC 200.

In one embodiment, the public key and/or certificate directory 210 isimplemented using an existing directory infrastructure provided, forexample, by VeriSign, Inc. of Mountain View, Calif. In alternateembodiments, the public key/certificate directory 210 is implementedusing a conventional database system, such as one available from SyBase,Inc. of Emeryville, Calif. In the prior example, the directory 210 maybe accessible by the general public, including sender 100 and recipient300. In the latter example, the directory 210 maybe accessed only by theOC 200. Preferably, the public key/certificate directory 210 is accessedby a directory interface 201 (not shown for the sender 100 and receiver300) using the Lightweight Directory Access Protocol (“LDAP”) and issearchable by client 899 registered email address, account name, and/orOC account number. Regardless of implementation of the directoryservice, the OC 200 uses the public keys in the directory toauthenticate clients, and provides key exchange functions forauthenticated clients. Key exchange is essential so sender 100 maytransparently obtain the public key of recipient 300.

In one embodiment, the OC 200 also operates the key management functions(of issuance, directory maintenance, key retrieval and exchange, keylife cycle maintenance) described above. It is beneficial for the OC 200to handle the complexities involved in key issuance, certification,storage, searching, rollover, etc. Because the OC 200 acts as a centralkey manager, it can implement and control the practices related to thekey, such as periodically facilitating the new issuance of key pairs tomaintain the integrity of keys. Also, since the OC 200 maintains thepublic keys/certificates, the OC 200 can perform real-time keyrevocation. Real-time revocation prevents communications from being sentusing compromised or invalid keys. Furthermore, since the OC 200maintains the public keys/certificates, a sender 100 needs to specifyonly a recipient 300's registered email address in order to obtain therecipient's public key.

In an alternate embodiment, a trusted third party or trusted thirdparties perform aspects of the public key/certificate management onbehalf of the OC 200. For example, a trusted third party could issue andmaintain digital certificates. When a sender 100 wants to send a messageto a recipient 300, the OC 200 would obtain the recipient's public keycertificate from the third party rather than maintaining the certificateitself. One skilled in the art will be aware that key and certificatemanagement can be handled by trusted third parties without deviatingfrom the spirit of this invention.

As depicted in FIG. 3, a sending system 100 facilitates the secure andreliable transmission of an electronic document 3 to the next recipient300 on a routing list for the document using the OC 200. Software forimplementing this sending system 100 can be supplied on acomputer-readable medium, such as with the registration software, or canbe received from the OC 200 via a network connection. As described inmore detail below, the sending system 100 authenticates a sender and theOC 200, creates a reliable connection 2A between the sender 100 and theOC 200, the OC 200 identifies the next recipient 300 on the routinglist, and the OC 200 provides a key or keys to the sender 100 which thesender 100 uses to secure the document 3 before it is transmitted to therecipient 300.

A sender uses the sending system 100 to send an electronic document 3 tothe recipient's receiving system 300 by connecting to the OC 200 througha network connection 1A. In one embodiment, a direct line between theparties 100, 200 provides reliability and security, but direct networkconnections are costly and in many instances impractical.

In an alternate embodiment, the sender 100 connects to the OC 200 via anetwork connection 1A, such as the Internet. Once connected to the OC200, the sender 100 begins the strong authentication (e.g. passwordprotection plus asymmetric key authentication) process by enteringher/his username and password, which the sender 100 selected as part ofthe registration process described above. The account profile module 101verifies the sender 100's username and password. If the username andpassword are correctly entered, the account profile module 101 grantsaccess to the sender 100's private key and the strong authenticationprocess 455 (FIG. 4) continues.

The sending system 100 automatically continues the strong authenticationprocess 455 by use of an authentication module 102. Since thisauthentication process is automatically performed, it is transparent tothe sender 100. The sender's authentication module 102 authenticates 455the sender 100 to the OC's authentication module 202 by sending the OC200 a digital signature generated using the sender's private key, thusproving that the sender 100 is who he claims to be.

The digital signature may be generated in many ways. In one approach,the sender simply encrypts some meaningful data using his private keyand sends this to the OC 200. If the OC 200 can use the sender 100'spublic key to decrypt the received data package, the OC 200 knows thatthe sender 100 is the one who encrypted the data package.

In a second approach, the sending system 100 randomly generates somedata to digitally sign. A hash algorithm creates a message digest, orhash, of the randomly generated data. A hash algorithm is a method oftransforming a variable length message, in this case the randomlygenerated data, into a fixed length number. This fixed length number isreferred to as the hash or message digest of the original message. Forthis message digest to be useful as part of a digital signature, thecontents of the message must not be practically ascertainable from themessage digest number. Thus, hash algorithms are typically one-wayfunctions, which can easily generate a hash from a message, but whichcannot, for all practical purposes, generate the original message giventhe hash. The message digest's usefulness as a digital fingerprint of amessage also depends upon its ability to correlate uniquely to theoriginal message. Ideally, a hash algorithm is a strictly one-to-onefunction so that each hash number can only be generated by one, and onlyone, message. Any change in the message, no matter how insignificant,will generate a different hash number. If a hash algorithm generates thesame hash for two different messages, a collision exists which couldcompromise the usefulness of the hash. Thus, one measure of a hashalgorithm's usefulness is the frequency at which more than one messagewill generate the same hash number. In practice, useful hash algorithmsmay generate collisions in theory but the probability is low enough asto be practically negligible. Well-known one-way hash algorithms thatare useful for digital signing include MD2, MD5, and SHA-1.

The hash of the randomly generated data, along with information aboutthe hash algorithm used to generate the hash, is then encrypted with thesender's private key. The sending system 100 sends the original randomlygenerated data as well as the encrypted hash to the OC 200. The OC 200uses the sender's public key to decrypt the hash. The OC 200 obtains thesender's public key by searching the public key directory 210. To verifythe integrity of data, the OC 200 uses the same hash algorithm on theoriginal randomly generated data. If the hash generated by the OC 200does not match the decrypted hash, this indicates a problem. The digitalsignature may not have been created with the sender's private key or thedata may have been tampered with since it was signed by the sender 100.If the hashes match, the OC 200 can be reasonably assured that thesender 100 sent the message.

Once the OC 200 has strongly authenticated 455 the identity of thesender 100, the sending system 100 can optionally authenticate theidentity of the OC 200. The OC 200's authentication module 202authenticates to the sending system's authentication module 102 in asimilar manner as the sender 100 was authenticated, that is, bydigitally signing some randomly generated data. The sending system 100obtains the OC 200's public key by searching the public key directory210. Alternatively, the sending system 100 could obtain the OC 200'spublic key in some other manner, such as having it coded into thesending system 100.

After the mutual strong authentication, a secure connection 2A isestablished 460 between the parties 100,200. A direct line can provide areliable and secure connection between the parties 100,200; however,direct lines are expensive and are not always available. In the exampleof FIG. 3, the secure connection 2A is established 460 by use of avirtual private network (“VPN”) or an SSL connection. A VPN connection2A could utilize protocols designed for layer 2 of the Open SystemsInterconnection (“OSI”) network architecture model, such as the Layer 2Tunneling Protocol (“L2TP”) or Point-to-Point Tunneling Protocol(“PPTP”). Alternately, the VPN connection 2A could be established usingan OSI layer 3 protocol such as IP Security protocol (“IPSEC”).Alternatively, the VPN could be established at one of the layers in thehost process subset (layers 5 through 7) of the OSI network architecturemodel. One benefit of establishing a VPN connection 2A at the hostprocess subset layers is that present VPN systems employ protocols inlayers 2 and 3. If the sender's computer system 100 is part of a networkthat already utilizes a VPN, a conflict may be created between theexisting VPN and the VPN connection 2A attempting to be established 460between the sending system 100 and the OC 200. By creating a VPNconnection 2A at the host process subset layers, the sender 100 and theOC 200 can establish a VPN independent of any other VPN used by sender100's network.

In one approach, the VPN connection 2A is created at the applicationlevel by using a session key and Hypertext Transfer Protocol (“HTTP”),Transmission Control Protocol (“TCP”), or File Transfer Protocol(“FTP”). The secure connection modules 103 and 204 establish the VPN, byperforming the following functions. Either the sending system's module103 or the OC 200's module 204 generates a session key. Once a sessionkey has been generated, the key-generating party transmits it via thenetwork connection 1A to the other party by encrypting the session keywith the receiving party's public key. For example, the sending system'ssecure connection module 103 generates a session key and encrypts itwith the OC 200's public key. The encrypted session key is transmittedto the OC 200's secure connection module 204, which decrypts the sessionkey. Once both parties have the session key, they communicate via a VPNconnection 2A that encrypts the application data with the session key.This process allows a compatible VPN tunnel to be created regardless ofexisting VPN setup in the sending system 100, as described incommonly-assigned U.S. Provisional Patent Application No. 60/242,015,“Application VPN with Application Proxies,” by Eng-Whatt Toh, filed 19Oct. 2000 and commonly-assigned U.S. patent application Ser. No.09/978,113, “Cryptographically Secure Network,” by Eng-Whatt Toh, etal., filed 15 Oct. 2001, which subject matter is incorporated herein byreference in its entirety.

The VPN connection 2A has many advantages. One advantage is that datatransmissions that occur over the VPN connection 2A carry additionalencryption since they have been encrypted by the VPN encryption key(i.e., the session key). Second, the VPN 2A creates a reliableconnection between the sender 100 and OC 200. Traditional Internet emailcommunications are routed through several email servers, which are ownedand operated by a number of parties. Since no single company or entityowns the entire delivery chain for the email, no one company or entitycan guarantee reliable delivery or integrity of the message. The VPN 2Aformed between the sending system 100 and the OC 200 creates apoint-to-point connection and is not forwarded through any Internetemail servers. This method is much more reliable than traditionalInternet email and allows the OC 200 to guarantee delivery of anymessage regardless of message type or size. In addition, it does notcreate an unnecessary audit trail.

As a final example, the VPN-enabled OC 200 acts as central switch thatcan effectively extend the VPN connection 2A from the sending system 100to the receiving system 300. Since a VPN connection is point-to-point,it is infeasible to produce a dynamic VPN connection that allows everypossible sender 100 to create a VPN to every possible recipient 300,without having a central key manager such as the OC 200. However, thisresult can in effect be achieved by having the OC 200 act as a centralswitch between sending system 100 and receiving system 300. Each client,whether sending an electronic document or receiving one, connects to theOC 200 by forming a VPN tunnel 2A,2B. In this manner, a VPN connection2A,2B is effectively created from the sending system 100 to thereceiving system 300 via the OC 200. This structure enables the OC 200to connect any sender 100 with any recipient 300 using a secure andreliable delivery system.

In steps 462 and 464, the OC 200 receives an indication that the senderdesires to deliver the document 3 to a next stage on a routing list forthe document and identifies a recipient 300 from the next stage. Theterm “stage” is different from “recipient.” For example, each stage mayinclude more than one recipient. The recipients may come from differentorganizations and may be located outside of each other's internalnetwork (e.g., outside of each other's firewall). Thus, the document maybe transmitted over the Internet between the various recipients, butstill with both security and reliability. FIGS. 10A-10C depict someexample routing lists.

FIG. 10A depicts a simple routing list which consists of a chain ofindividuals. In this routing list, the document is to be routed fromindividual A to B to C to D. Each individual recipient represents adifferent stage on the routing list. Stage 1 includes individual A,stage 2 includes B, etc. The routing list is also given an identifier,which is “list 1” in this case. Thus, if the OC 200 receives 462 anindication that sender B would like to deliver the document 510 to thenext stage on routing list “list 1,” the OC 200 (specifically, therouting module 209) resolves the routing list to identify 464 individualC as the next recipient since the next recipient after B is C.

If the OC 200 is tracking progress of the document along the routinglist, it can also confirm that B is the current recipient of thedocument and that, therefore, a request from B to send the document tothe next recipient is consistent with its tracking of the document. Incontrast, if the OC 200's tracking indicates that A is the currentrecipient of the document, then a request from B to send the document tothe next stage on the routing list would be inconsistent. The OC 200would then take appropriate actions, for example declining B's requestto send the document to the next stage.

FIG. 10B depicts a routing list in which some of the stages includegroups of recipients. In this case, the document is to be routed fromindividual A (stage 1), to group B (stage 2), to group C (stage 3), toindividual D (stage 4). Group B contains recipients B1, B2, . . . Bn,and group C contains recipients C1, C2, . . . Cn. The routing ofdocuments to/from groups can be performed in a number of ways and istypically defined in the rules for the routing list, as is also shown inFIG. 10B.

In this example, when A is finished with the document, A forwards thedocument to the email address review.team@xyz.com. The OC 200 receivesthe indication 462 that the sending system 100 desires to send thedocument to the next stage. The OC 200 determines 464 that the nextstage after sender A includes all recipients in group B, and eventuallyreturns 480 or 475 the public keys required to deliver the document toall of the recipients in group B.

As each recipient in group B finishes with the document, it is routed toa corresponding member in group C. For example, when B1 is finished, hesends the document to review.team@xyz.com. Upon receiving thisindication 462 from B1, the OC 200 (specifically routing module 209)determines 464 that the next recipient following sender B1 is recipientC1. In subsequent steps 475 or 480, the OC 200 returns the appropriatepublic key for C1. That is, the document is routed to C1 when B1finishes, to C2 when B2 finishes, etc. Note that in this example, thereare equal numbers of recipients in groups B and C. For example, thepairs B1-C1, B2-C2, etc. may represent different two-person teams whichreview the document in parallel.

All members of group C must finish with the document before it is routedto the final recipient D. Continuing with this example, when C1 isfinished with the document, he forwards the document toreview.team@xyz.com. The sending system 100 sends this indication 462 tothe OC 200 that it desires to send the document to the next stage, uponwhich the OC 200 (specifically routing module 209) determines 464 thatthe next recipient is recipient D. In subsequent steps 475 or 480, theOC 200 returns the appropriate public key for D. However, the OC 200stores 530 the delivery in the storage area 205 until all members ofgroup C are finished, as is dictated by the rules.

For convenience, the routing list identifier “review.team@xyz.com” is anemail address. Thus, senders can use the routing list by sending theirdocument to this special email address. Emails sent to this address arerouted to the routing module 209, which resolves the email address to anext recipient(s). One advantage of this approach is that conventionalemail servers can then support routing lists as addressees withoutproblems.

FIG. 10C is a final example of a routing list which includes rules thatembody a business process involving the sales and marketing departmentof a company, the company's outside law firm and external creditagencies. In this case, the rules for the routing list embody companyxyz's process for approving orders from new customers. In oneimplementation, the rules embodying xyz's approval procedure areencapsulated as part of a routing form and provided to the routingmodule 209 as part of the indication to deliver document 462. Therouting list is named “newsales@routinglists.xyz.com.” The domain name“routinglists.xyz.com” has been set aside for routing lists.

The routing list operates as follows. A salesperson initially completesthe routing form which may contain, among other information, the valueof the transaction and his sales territory. The sales person sends therouting form together with a purchase order from a new customer to therouting list for approval. The first stage of the routing list is thesalesperson's regional sales manager in the corporate head office, whomust approve the transaction before it can advance to the next stage.Note that stage one includes a group of potential recipients since thereis more than one regional sales manager. The sales person starts bysending the purchase order and the routing form tonewsales@routinglists.xyz.com. The sending system 100 sends indication462 including the routing form to the OC 200 that it desires to send thedocument to the next stage, upon which the routing module 209 of OC 200determines 464 the sales manager corresponding to the sales person usinginformation provided in the routing form. In subsequent steps 475 or480, the OC 200 returns the appropriate public key for the salesmanager. In this way, the routing form and purchase order can besecurely and reliably routed to the correct regional sales manager.

Upon the sales manager's approval, the purchase order is routed to anexternal credit agency, which must also approve the transaction. Thesales manager indicates approval by digitally signing the routing formand the purchase order, and then sends the routing form with thepurchase order to newsales@routinglists.xyz.com. In an alternateembodiment, the approval is reflected in the document itself. Forexample, the sales manager might digitally sign only the purchase orderor place a tracking code onto the purchase order. In anotherimplementation, the approval is transmitted separately between the salesmanager and the OC 200. For example, the OC 200 may query the salesmanager whether he approves the purchase order.

Returning to this example, when the sales manager is ready to route thepurchase order and routing form; the sending system 100 sends anindication 462 including the routing form to the OC 200 that it desiresto send the purchase order to the next stage. Upon receiving the requestand the routing form, the routing module 209 of OC 200 determines 464that the digital signature on the routing form is valid and selects anindividual in the credit agency as a next recipient. In oneimplementation, the routing module 209 selects one of the individualsaccording to xyz's internal rules. For example, routing module 209 mayselect the individual which will give the fastest response time, or theindividual who is assigned to the specific sales region. In anotherimplementation, the routing module 209 sends the purchase order to allof the qualified individuals at the credit agency but only requires oneapproval before moving to the next stage. Regardless of the specificmethod, the routing module 209 determines 464 the recipients for stagetwo, and subsequently returns 475 or 480 the appropriate keys for thenext recipient(s).

In stage three, the purchase order and routing form are routed to both aVP level executive and xyz's law firm for separate approvals, but onlyif the amount of the purchase order is over $100,000. Stage three is anexample of conditional recipients. The VP and law firm receive thepurchase order only if certain conditions are met (if the amount is over$100,000 in this example). Whether the condition is met may bedetermined in a number of ways. For example, the amount of the purchaseorder may be transmitted with the purchase order or routing form or theOC 200 may query earlier recipients as to the amount of the purchaseorder. In other examples, different parameters may be transmitted withthe purchase order and/or affect routing of the document. After stagethree, the purchase order has been approved. It is then routed to boththe accounting department and the shipping department for orderfulfillment and payment collection. Note that the purchase order wouldgo directly to stage four if the amount was less than $100,000.

Continuing with the above example, the credit agency countersigns therouting form and the purchase order and sends them tonewsales@routinglists.xyz.com. The sending system 100 sends indication462 including the routing form to the OC 200 that it desires to send thedocument to the next stage. The routing module 209 verifies that therouting form has been signed by the credit agency and decides who thenext recipients are depending on the transaction amount provided in therouting form. In subsequent steps 475 or 480, the OC 200 returns theappropriate public keys.

The routing lists shown in FIG. 10 are merely examples. Other types ofrouting lists and rules will be apparent. Another example rule is thatdifferent recipients receive different versions of the document, perhapsa read-only version or the document in different formats to accommodatedifferent applications. In addition, steps 462 and 464 are shown in FIG.4 as occurring after step 460. However, this order is not required. Inan alternate implementation, the OC 200 receives 462 an indication ofthe sender's wish to deliver the document to the next stage on therouting list and resolves 464 the routing list to a next recipientearlier in the flow diagram (e.g., before step 460).

The indication 462 from the user may take any number of forms. Forexample, the OC 200 may receive the document together with the routinglist through the secure connection 2A. Alternately, the sender may querythe OC 200 for the next stage of the routing list. As part of the query,the sender may further provide a routing form comprising the routingrules and routing parameters that may determine who the next recipientsare, as highlighted in the example of FIG. 10C.

In one implementation, the OC 200 tracks the current recipient of thedocument. For example, referring to FIG. 10C, tracking of the purchaseorder might indicate that purchase order #1234 currently resides withthe regional sales manager for the Northeast region. The OC 200 thenresponds to the sender's query for the next stage of the routing list byreturning the identity of a next recipient from the routing list if thequerying sender is the current recipient (i.e., if the querying senderis the Northeast region sales manager). On the other hand, the OC 200sends an error message if it cannot resolve the query (e.g., if therouting list for the document cannot be located or if the queryingsender is not the Northeast region sales manager). In one approach, theOC 200 waits until it receives confirmation that the next recipient hasreceived the document before updating its tracking of the document.Continuing the above example, the OC 200 would wait for confirmation ofreceipt from the credit department before changing the current recipientfrom the regional sales manager to the credit department.

Routing lists may also be set up in a number of ways. For example, arouting list may be defined a priori (i.e., before anyone actually triesto use the routing list) and then stored for subsequent use. The routinglist in FIG. 10C is a good candidate for this approach since it israther complicated (both in terms of lists of recipients and the rulesgoverning the routing list) and likely would require multiple approvalswithin company xyz before it could be established. On the other hand,the routing lists in FIGS. 10A-10B are simple enough that they could bedefined by the first sender who wishes to use the routing list. In oneimplementation, the originating sender sends the routing list along withits indication to deliver a document to the routing list. The OC 200receives the routing list in order to process the document. The OC 200may also store the routing list for subsequent use. Once the routinglist is set up, the routing module 209 of OC 200 can securely routedeliveries by returning the correct public keys for the nextrecipient(s) on the routing list. It can determine the next recipient(s)in a number of ways, including using information provided in a routingform and/or by tracking the current recipient along a routing list.

Returning to FIG. 4, once the secure tunnel 2A is formed between thesending system 100 and the OC 200, the sending system 100 obtains therecipient 300's public key. In one implementation, the sender 100 sendsthe delivery 510 to the OC 200 through the secure tunnel 2A. This couldserve as the indication 462 to deliver the document. In thisimplementation, the OC 200 encrypts the delivery 510 using the selectedrecipient 300's public key and proceeds with step 535 (to be describedlater). This implementation is advantageous in that the sending system100 is simpler and smaller with reasonable security since the delivery510 is protected by the secure tunnel 2A. However, this does not provideend-to-end security or digital signatures.

In a preferred implementation, the OC 200 resolves 464 the routing listand returns the identity of the next recipient 300 to the sending system100. The sending system 100 can then obtain the recipient 300's publickey by searching the public key directory 210. Alternatively, thesending system 100 queries 465 the OC 200 for the recipient 300's publickey 404. Alternatively, the OC 200 resolves the routing list 464 andreturns 465 the recipient 300's public key 404 all in one step. Therouting module 209 resolves the routing list and a directory interface201 obtains 480 the recipient 300's public key 404 from the public keydirectory 210, which is transmitted 485 to the sending system 100 viathe secure connection 2A, typically in the form of a digital certificatefrom the public key directory 210. The key management module 205monitors the public keys to ensure that the OC 200 returns to thesending system 100 the recipient 300's current public key 404.

The foregoing explanation assumed that the recipient 300 has a validpublic key 404. The recipient 300 may not have a valid public key, forexample, if the recipient 300 has not registered with the OC 200 priorto the sending system 100 transmitting the document 3, or if therecipient 300's public key has been revoked for some reason. In eithercase, when the sending system 100 requests 465 the recipient 300'spublic key, none will exist. To solve this problem, the OC 200 and/orthe escrow manager 211 can securely hold the message in escrow until therecipient 300 registers with the OC 200 or until a new public-privatekey pair is generated. When the sending system 100 requests 465 therecipient 300's public key and none is found in the public key directory210, the escrow manager 211 provides 475 an escrow encryption key 406,which is transmitted 485 to the sending system 100.

Whether the sending system 100 receives the recipient's public key 404or an escrow encryption key 406, the sending system 100 uses the key 404or 406 to secure the document 3. In one embodiment, the sending system'sencryption module 104 encrypts 490 the document 3 using whichever key404 or 406 was transmitted 485 to it. Alternatively, instead ofencrypting the document with the public key 404 or escrow encryption key406, the sending system's encryption module 104 could encrypt thedocument 3 using other cryptographic standards, for example, Public KeyCryptography Standard #7. That is, the sending system 100 uses adocument encryption key 410 to encrypt the document 3, and uses theescrow encryption key 406 or recipient public key 404 to encrypt adocument decryption key 412. The document encryption key 410 is a key,preferably generated by the sending system 100, which the sending system100 uses to encrypt the document 3. Preferably, the document encryptionkey 410 is a symmetric key (in which case the document encryption key410 and the document decryption key 412 are the same key) because of itsreduced time requirements needed for the encryption/decryption processas compared to asymmetric keys. But alternatively, the documentencryption key 410 could be an asymmetric key. In the case of anasymmetric document encryption key 410, the sending system 100 willencrypt the document 3 with the document encryption key 410 and willinclude the document decryption key 412 encrypted with the recipient'spublic key 404 or encrypted with the escrow encryption key 406 as partof the delivery 510. In either case, the escrow encryption key 406 orthe recipient's public key 404 is used for encrypting 490 the documentdecryption key 412 rather than encrypting the document 3.

The delivery 510 to be transmitted to the recipient 300 comprises atleast the encrypted document 3. The delivery may also include anencrypted document decryption key 412, if a document encryption key 410was used to encrypt the document 3. If an escrow encryption key 406 wasemployed by the sending system 100, the OC 200 or escrow manager 211 mayalso include the escrow decryption key 407 as part of the delivery 510although this generally is not recommended. The delivery 510 can alsoinclude addition data. For example, the delivery 510 can include a coverletter or message, the header information of an email message (forexample, the sender 100 and the recipient 300 names or aliases, emailaddresses of the sender and the recipient, message “Re:” data, and soforth), and tracking information, such as a unique tracking number. Thedelivery can also include one or more message digests, such as a messagedigest of the document 3, and one or more digital signatures, such adigital signature of the sender 100. The message digests and/or digitalsignatures allow for sender authentication, non-repudiation, and messageintegrity. For example, the document 3 can be digitally signed. Thedigital signature allows for sender authentication. The digitalsignature can be generated in a similar manner as described above duringthe authentication phase. Alternatively, the sending system 100 candigitally sign the document 3. In another alternative, the contents ofthe document 3 are mathematically hashed using a one-way hash functionto create a message digest or hash number. The hash number is thenencrypted using the sender 100's private key 401. This encrypted hashnumber serves two functions. First, it functions as a digital signature.Second, the hash number can be used to verify that the document 3 wasnot altered during transmission. Once the receiving system 300 receivesand decrypts the document 3 and the hash (if it was sent in encryptedform), the receiving system 300 hashes the document 3. If the hashnumbers match, then the document 3 was not altered. This latterembodiment allows for non-repudiation by the sender 100 because thedocument 3 arrived signed and unaltered. The above-mentioned items canbe encrypted in the same manner as the document 3 and delivered as partof the delivery 510. Transmission of the delivery 510 to the recipient300 can occur in a number of ways, which will be detailed below.

Referring now to FIG. 3 and FIG. 5, if the recipient 300 does not accept495, 525 direct transfer of the delivery 510, the OC 200 can act as astaging area for the delivery 510. The OC 200 receives 530 the delivery510 from the sending system 100 via the first secure connection 2A. TheOC's messaging module 203 receives the delivery 510, and the OC 200stores 530 the delivery 510 in a storage area 206.

The OC 200 notifies 535 the recipient 300 that a delivery 510 has beenaddressed to the recipient 300 and awaits transmission pending secureconnection with the OC 200. The recipient 300 could be notified byemail, facsimile, telephone, courier or mail service, or the like. Inthe embodiments in which an escrow encryption key 406 is used as part ofthe delivery 510 encryption process, before the recipient can receivethe delivery 510 from the OC 200, the recipient 300 must register 543with the OC 200 and provide an existing key-pair or must generate 543 anew key pair. The registration of the recipient 300 occurs in the samemanner as described above for the client 899 (see FIG. 8). To generate anew key pair, the key manager module 205 prompts the key registrationmodule 305 to generate a new private-public key pair (403,404—respectively). The public key 404 is transmitted to the OC 200, isassociated with the recipient 300, and is stored in the public keydirectory 210 for use with future deliveries. The recipient accountprofile 301 is updated to include the current private key 403. In theembodiments in which the recipient had a valid public key 404 which wasused as part of the delivery 510 encryption process, the recipient 300can proceed to receive the delivery 510 from the OC 200.

With its valid key pair 403, 404, the recipient 300 can obtain thedelivery 510 from the OC 200. The recipient 300 accesses its private key403 stored in the account profile module 301, such as by entering anaccount name and password, and connects to the OC 200 via a networkconnection 1B. In the same manner as discussed above for the sendingsystem 100, the receiving system 300 strongly authenticates 545 to theOC 200 and, optionally, the OC 200 strongly authenticates to thereceiving system 300. As with the sending system 100, a secureconnection 2B, such as an SSL connection or a point-to-point VPN tunnel,is formed 550 between the OC 200 and receiving system 300. The receivingsystem 300 can then request the delivery 510. The OC 200's messagingmodule 203 transmits 555 the delivery 510 from the OC 200's storage area206 to the receiving system 300 via the secure connection 2B. Thereceiving system's encryption/decryption module 304 decrypts 560 thedocument 3 to return it to an intelligible form.

The process of decrypting 560 the document 3 depends upon the methodemployed by the sending system 100. If the sending system 100 encryptedthe document 3 with the recipient's public key 404, the receiving system100 decrypts the document 3 using the recipient's private key 403. Ifthe sending system 100 encrypted the document 3 using a documentencryption key 410, the receiving system 300 uses its private key 403 todecrypt the document decryption key 412 and then uses the documentdecryption key 412 to decrypt the document 3.

In the embodiments in which an escrow encryption key 406 was used by thesending system 100, the OC 200 or escrow manager 211 could transmit 555the escrow decryption key 407 as part of the delivery 510 to thereceiving system 300. Alternatively, the OC 200 or escrow manager 211could decrypt the document 3 and re-encrypt it with the recipient 300'spublic key 404 prior to transmitting 555 it to the recipient 300. Inanother embodiment, the sending system 100 uses a document encryptionkey 412 to encrypt the document 3. The sending system 100 encrypts thedocument decryption key 412 using the escrow encryption key 406, whichcould represent the escrow manager's public key, which the sendingsystem 100 obtains from one of the following: its own encryption module104, the public key directory 210, the OC 200, and the escrow manager211. The sending system 100 transmits the encrypted document 3 and theencrypted document decryption key 412 to the OC 200 or the escrowmanager 211 as the delivery 510. When the recipient 300 requests thedelivery 510, the OC 200 or escrow manager 211 decrypts the documentdecryption key 412 using the escrow decryption key 407, which couldrepresent the escrow manager's private key, and re-encrypts the documentdecryption key 412 with the recipient 300's public key 404. Then, theescrow manager 211 or OC 200 messaging module 203 sends the delivery510, which includes the re-encrypted document decryption key 412 to thereceiving system 300. The receiving system 300 then decrypts thedocument decryption key 412 with its private key 403 and uses that key412 to decrypt the document 3.

For examples of key escrow systems, see commonly-assigned U.S.Provisional Application Ser. No. 60/242,014, “Method For Fast EscrowDelivery,” by Chee-Hong Wong, Kok-Hoon Teo, See-Wai Yip, and Eng-WhattToh, filed 19 Oct. 2000, and commonly-assigned U.S. patent applicationSer. No. 09/332,358, “Simplified Addressing for Private Communications,”by Eng-Whatt Toh and Peng-Toh Sim, filed 10 Jun. 1999, which subjectmatter is incorporated herein by reference in its entirety.

The decryption module 304 can also decrypt (if encrypted) and verify 565the digital signature and message digests, if those items are includedwith the delivery 510. In order to verify the digital signature, thedecryption module 304 uses the sender 100's public key. The decryptionmodule can obtain the sender 100's public key by accessing the publickey directory 210, by receiving it as part of the delivery 510, or byrequesting the public key from the OC 200. The OC 200 can retain thesender 100's public key from the authentication processes with thesending system 100; or alternatively, the OC 200 can obtain the sender100's public key by searching the public key database 210. The receivingsystem 300 could also optionally notify 570 the OC 200 of the results ofthe verification of the integrity and/or digital signatures.

In FIGS. 6 and 7, alternate embodiments are depicted in which thereceiving system 300 accepts 525 direct transfer. In the previousembodiments, the entire delivery 510 was sent via the OC 200. In thealternate embodiments of FIGS. 6 and 7, the delivery 510, or a largeportion 505 (See FIG. 9) of it, is sent directly from the sending system100 to the receiving system 300 rather than via the OC 200. Theseembodiments are advantageous because they reduce the volume of data thatflows through the OC 200. As with the previous embodiments, the OC 200still acts as a central key manager by providing the keys necessary toensure proper authentication, secure connection setup, encryption, andthe like.

FIG. 6 depicts peer-to-peer embodiments wherein the sending system 100transmits the delivery 510 directly to the receiving system 300 via adirect and secure connection 2C (FIG. 9), such as a peer-to-peer VPNconnection or SSL connection. For example, the sending system 100queries 525 the OC 200 to ascertain the receiving system 300's identity(from resolution of the routing list) and to determine if the receivingsystem 300 accepts direct transfers. The OC 200 can determine if thereceiving system 300 is available to accept a direct delivery by, forexample, determining if the receiving system 300 is presently connectedto the OC 200. If the receiving system 300 is available to accept adirect delivery and is connected to the OC 200, the sending system 100is notified 624 by the OC 200 and initiates 626 a secure connection 2Cbetween the sending system 100 and the receiving system 300. Preferably,the secure connection 2C is an SSL connection or a peer-to-peer VPNconnection. Alternatively, the OC 200 could notify 614 the recipient 300that the sender 100 has a delivery 510 pending, and the receiving system300 initiates 616 a secure connection 2C with the sending system 100.

With the direct and secure connection 2C established, the sending system100 transmits 630 the delivery 510 to the receiving system 300.Optionally, the OC 200 exchanges acknowledgements 635 with sending andreceiving systems 100, 300 that transfer 630 of the delivery 510 wassuccessful. These acknowledgements could include acknowledgements of thetracking items discussed below.

With the delivery 510 transferred to the receiving system 300, thereceiving system's encryption/decryption module 304 decrypts 640 thedocument 3. Optionally, the delivery 510 or document 3 integrity isverified 645, as well as verification of any digital signatures whichwere included as part of the delivery 510. The receiving system 300could also optionally notify 650 the OC 200 of the results of theverification of the integrity and/or digital signatures.

If the receiving system 300 does not accept direct deliveries or isotherwise unavailable to presently accept the delivery 510, the sendingsystem 100 has at least two options. The first option is the set ofembodiments described above with reference to FIG. 5. Thus, the sendingsystem 100 sends all of the delivery 510 via the OC 200, as previouslydescribed. Alternatively, the sender 100 can notify the recipient 300that the sender has a delivery 510 which the sender 100 wishes totransmit via a direct and secure connection 2C. The recipient 300 canthen connect to the sender 100 when it is ready to do so.

FIG. 7 depicts an embodiment for sending the delivery 510 via a directand secure connection 2C (FIG. 9), such as a peer-to-peer VPN connectionor SSL connection, when the receiving system 300 will accept directtransfer but is not presently available to receive the delivery 510. Thesending system 100 notifies 700 the OC 200 that the sending system 100has a delivery 510 for the receiving system 300. The OC 200 notifies 705the recipient 300 that the sender 300 has a pending delivery 510. Therecipient connects 710 to the OC. If necessary, the recipient 300registers 543 with the OC 200, as explained above in reference to FIG.8, or generates 543 a new private-public key pair 403,404—respectively,which has also been detailed above in reference to FIG. 5.

With its valid key pair, the recipient strongly authenticates 715 to theOC 200. Optionally, the OC 200 can authenticate to the receiving system300. A secure connection 2B is established 720 between the receivingsystem 300 and the OC 200. The receiving system 300 initiates a secureconnection 2C between itself and the sending system 100. With the securepeer-to-peer connection 2C established, the receiving system 300retrieves the delivery 510 from the sending system 100. Optionally, theOC 200 exchanges acknowledgements 735 with sending and receiving systems100,300 that the delivery transmission was successful. Theseacknowledgements could also include acknowledgements of the trackingitems discussed below.

With the delivery 510 transferred 730 to the receiving system 300, thereceiving system's encryption/decryption module 304, decrypts 740 thedocument 3. Optionally, the delivery 510 or document 3 integrity isverified 745, as well as verification of any digital signatures whichwere included as part of the delivery 510. The receiving system 300could also optionally notify 750 the OC 200 of the results of theverification of the integrity and/or digital signatures.

As graphically depicted in FIG. 9, alternative embodiments of the abovepeer-to-peer embodiments involve at least a portion of the delivery 500,such as a packet, the header information, the last byte of the delivery510, or the decryption key or keys required to decrypt the delivery 510or the document 3, being sent via the OC 200. The portion of thedelivery 500 can be any portion of the delivery 510, recalling that thedelivery includes at least the document 3, but which could also includeadditional data as explained previously.

The embodiments described above in reference to FIG. 6 and FIG. 7 can bereadily adapted so that a portion of the delivery 500 is sent via the OC200, and the remainder of the delivery 505 is transmitted directly fromthe sender 100 to the recipient 300 via a direct and secure connection2C. For example, the query 495 received by the OC 200 from the sendingsystem 100 could include the small portion of the delivery 500 that isnecessary to complete or to open the delivery 510. For example, the OC200 can transmit this portion of the delivery 500, with the notice tothe recipient 300 of the pending delivery, such as at step 614 or 705.Furthermore, the OC 200 could also transmit the portion of the delivery500 prior to the recipient 300 receiving the remaining portion of thedelivery 505, or the OC could transmit portion of the delivery 500 afterthe recipient 300 has acknowledged receiving the remaining portion ofthe delivery 505, such as at step 635,735.

These embodiments are advantageous because the OC 200 does not need torely entirely on the notifications/acknowledgments 635,735 sent by thesending system 100 and receiving system 300 to track the transmission ofthe delivery 510. Because a portion of the delivery 500 is sent via theOC 200, the OC 200 can track and time-stamp the portion of the delivery500 just as it would track the delivery 510, if the entire delivery 510were transmitted via the OC 200. The OC's 200 involvement intransmitting the portion of the delivery 500 mitigates problems when thenotifications of the transmission and receipt of the delivery 510 arealtered or not sent by either the sending or receiving systems 100,300respectively. With the OC 200 at least partially involved in thetransmission of the delivery 510, neither party 100,300 can repudiatethe delivery 510 and the tracking.

As mentioned above, in addition to securely and reliably transmittingthe delivery from the sender 100 to the recipient 300, the aboveembodiments can also include delivery 510 tracking and notification.Tracking features are implemented by the tracking module 208 andinclude, for example, time-stamping the document 3 at main pointsthroughout the delivery process. The main points through the deliveryprocess could include the time at which the delivery 510, or a portionof it 500, was transmitted to the OC 200 or the escrow manager 211; thetime at which the recipient 300 received the delivery 510, or anyportion 500,505 of it; and the time at which the recipient 300successfully decrypted the document 3. For example, when the sendingsystem 100 transmits the delivery 510, or any portion thereof 500, tothe OC 200, a tracking module 208 assigns a unique tracking number tothe delivery 510, or any portion thereof 500, and time stamps it. Thetracking module 208 then tracks the delivery 510, or any portion thereof500, throughout the delivery process. Tracking information can also beused to update the OC 200's record of which recipient on a routing listfor a document is the current recipient.

Another feature that can be performed by the OC 200 is the notificationprocess. For example, the OC 200 can notify the recipient 300 that adelivery 510 has been received or is pending at the sender 100. Once thedelivery 510 has been transmitted to the OC 200 or to the escrow manager211, the messaging module 203 notifies the recipient 300 that a delivery510, or at least a portion of the delivery 500, has been received. In analternate embodiment, the messaging module 203 alerts the recipient 300of the waiting delivery 510, or any portion thereof 500,505, by emailnotification, using for example, the email address supplied during theregistration process. However, those skilled in the art will recognizethat other notification systems and methods could be used withoutdeparting from the spirit of the invention. For example, the receivingsystem 300 may include a notification client (not shown) that receivesuser datagram protocol (“UDP”) notifications from the messaging module203. Upon receipt of UDP notifications, the notification clientgenerates an audible or visual desktop notification, such as a chime, ablinking icon, a pop-up dialog box, or the like. Other forms ofnotification could include voice notification via a voice synthesismodule, a pager notification, or a facsimile notification.

The sender 100 can likewise obtain notification. For example, the sender100 can be notified that a notice was sent to the recipient 300.Additional notifications can include notifying the sender 100 that therecipient 300 has received the delivery 510 or the at least portion ofthe delivery 500. The sender 100 could also be notified that therecipient 300 has decrypted the document 3. If a delivery 510, orportion of the delivery 500, was delivered to the OC 200 and remainedthere for a set time period, for example thirty (30) days, and was neverrequested by the recipient 300 to be delivered, a notification to thesender 100 can be sent to indicate that the delivery 510, or portionthereof 500, was never requested. Finally, a notification could be sentto the sender 100 indicating that the OC 200 was unable to transmit thedelivery 510, or the at least a portion of the delivery 500, to therecipient 300. The sending system 100 could receive notification in thesame manner as was described above for the receiving system 300.

Each of the above notifications can be time stamped by the OC 200 toprovide not only notice but also timing information. The tracking andnotification features, including the time stamping, allows for furthernon-repudiation because both the sender 100 and the recipient 300 cantrack the delivery 510 throughout its transmission. These features alsosupport the reliability of the present invention. Alternativeembodiments could use other notification and tracking features.

The above description is included to illustrate the operation of thepreferred embodiments and is not meant to limit the scope of theinvention. The scope of the invention is to be limited only by thefollowing claims. From the above discussion, many variations will beapparent to one skilled in the art that would be encompassed by thespirit and scope of the present invention.

1. A method for facilitating a secure delivery of a document from asender to a next stage on a routing list, the method comprising thesteps of: receiving an indication that a sender desires to deliver adocument to a next stage on a routing list for the document; identifyinga recipient from the next stage of the routing list; sending an inquiryto a public key database to determine whether the recipient has a publickey; receiving a response to said inquiry, said response selected fromthe group of said recipient having a public key in said database andsaid recipient not having a public key in said database; if saidresponse is said recipient having a public key in said public keydatabase, completing the steps of: (a) retrieving said public key fromsaid public key database and (b) setting a message encryption key forencrypting the document equal to said public key; (c) encrypting thedocument prior to sending said document using the message encryptionkey; if said response is said recipient not having a public key in saidpublic key database, completing the steps of: (a) providing an escrowencryption key not equal to the recipient's public key and not equal tothe sender's private key, wherein an escrow unencryption key forunlocking said escrow encryption key is not made available to saidrecipient and (b) encrypting the document using the generated escrowencryption key, and storing the escrow key encrypted document until anew public encryption key is assigned to the recipient; (c) assigning anew public encryption key not equal to the generated escrow encryptionkey and private encryption key to the recipient; (d) unencrypting theescrow encryption key encrypted document using an escrow unencryptionkey and re-encrypting the document using the new public encryption keyprior to sending said document using the message encryption key; andproviding the public key encrypted document to the recipient.
 2. Themethod of claim 1 further comprising: defining and storing the routinglist before an originating sender indicates a desire to deliver thedocument to the routing list.
 3. The method of claim 1 furthercomprising: receiving the routing list together with an indication thatan originating sender desires to deliver the document to the routinglist; and storing the routing list.
 4. The method of claim 1 furthercomprising: sending the message encryption key to the sender.
 5. Themethod of claim 4 wherein the step of sending the message encryption keyto the sender comprises: sending to the sender a digital certificatecontaining the recipient's public key.
 6. The method of claim 4 furthercomprising: the sender encrypting the document using the messageencryption key; and the sender delivering the encrypted document to therecipient.
 7. The method of claim 1 further comprising: the senderdelivering the document to the recipient.
 8. The method of claim 1wherein: the routing list is identified by a routing list identifier;and the step of receiving an indication that a sender desires to delivera document to a next stage on the routing list includes receiving therouting list identifier.
 9. The method of claim 8 wherein the routinglist identifier includes an email address of said routing list.
 10. Themethod of claim 8 wherein the routing list identifier includes anaddress at a domain name of a web page for routing lists.
 11. The methodof claim 1 wherein: the next stage in the routing list comprises a groupof recipients; and the step of identifying a recipient from the nextstage comprises identifying at least one of the recipients in the group.12. The method of claim 1 wherein the step of receiving an indicationthat a sender desires to deliver a document to a next stage on therouting list comprises: receiving a query from the sender for anidentity of a recipient from the next stage of the routing list.
 13. Themethod of claim 12 further comprising: tracking a current recipient ofthe document from the routing list; and in response to the query:returning an error message, if the routing list cannot be located or thequerying sender is not the current recipient; and returning the identityof at least one recipient from the next stage of the routing list, ifthe querying sender is the current recipient.
 14. The method of claim 1further comprising: tracking a current recipient of the document fromthe routing list.
 15. The method of claim 14 further comprising:receiving confirmation that the recipient has received the document; andupdating the current recipient of the document to reflect the receivedconfirmation.
 16. The method of claim 1 wherein the routing listincludes rules.
 17. The method of claim 16 wherein the rules areencapsulated in forms.
 18. The method of claim 16 wherein the rulesembody a business process.
 19. The method of claim 1 wherein the routinglist includes conditional recipients.
 20. The method of claim 19 whereinthe step of receiving an indication that a sender desires to deliver adocument to a next stage on a routing list for the document comprises:receiving a parameter from the sender, wherein the recipient depends onthe parameter received.
 21. The method of claim 1 wherein the step ofreceiving an indication that a sender desires to deliver a document to anext stage on a routing list for the document comprises: receiving aform containing rules for the routing list.
 22. The method of claim 1wherein the step of receiving an indication that a sender desires todeliver a document to a next stage on a routing list for the documentcomprises: receiving a routing parameter for the routing list.
 23. Themethod of claim 1 wherein the step of receiving an indication that asender desires to deliver a document to a next stage on a routing listfor the document comprises: receiving the document together with theindication.
 24. The method of claim 23 further comprising: deliveringthe document to the recipient.
 25. The method of claim 23 furthercomprising: delivering the document in read-only mode to the recipient.26. The method of claim 23 further comprising: encrypting the documentusing the message encryption key before delivering the document to therecipient.
 27. The method of claim 1 further comprising: authenticatingthe sender using the sender's public key; establishing a first secureconnection with the sender; and receiving the document from the sendervia the first secure connection.
 28. The method of claim 27 furthercomprising: authenticating the recipient using the recipient's publickey; establishing a second secure connection with the recipient; andtransmitting the document to the recipient via the second secureconnection.
 29. A computer program product for facilitating a securedelivery of a document from a sender to a next recipient on a routinglist, the computer program product comprising program code adapted toperform the steps of: receiving an indication that a sender desires todeliver a document to a next stage on a routing list for the document;identifying a recipient from the next stage of the routing list;searching for a public key for the recipient and setting asearch-dependent key for encrypting the document depending on theparameter of whether a recipient's public key was found; wherein saidkey is set equal to a public key of the recipient when the recipient'spublic key is found; and wherein said key is set equal to a generatedescrow encryption key not equal to the recipient's public key when therecipient's public key cannot be located; encrypting the document usingthe search dependent key; if the search dependent key is equal to thegenerated escrow encryption key, performing the additional steps ofassigning a new encryption key and a private encryption key to therecipient not equal to the generated escrow encryption key; unencryptingthe escrow encryption key encrypted document using an escrowunencryption key; and re-encrypting the document using the new publicencryption key; providing the encrypted document to the recipient. 30.The computer program product of claim 29 wherein said escrowunencryption key is not provided to the recipient.
 31. The computerprogram product of claim 29 wherein: the routing list is identified byan email address; and the step of receiving an indication that a senderdesires to deliver a document to a next stage on the routing listincludes receiving the email address.
 32. The computer program productof claim 29 wherein: the routing list is identified by an address at adomain name for routing lists; and the step of receiving an indicationthat a sender desires to deliver a document to a next stage on therouting list includes receiving the address.
 33. The computer programproduct of claim 29 wherein the step of receiving an indication that asender desires to deliver a document to a next stage on the routing listcomprises: receiving a query from the sender for an identity of arecipient from the next stage of the routing list.
 34. The computerprogram product of claim 29 wherein the program code is further adaptedto perform the step of: tracking a current recipient of the documentfrom the routing list.
 35. The computer program product of claim 29wherein the routing list includes rules.
 36. The computer programproduct of claim 35 wherein the rules are encapsulated in forms.
 37. Thecomputer program product of claim 35 wherein the rules embody a businessprocess.
 38. The computer program product of claim 29 wherein therouting list includes conditional recipients.
 39. The computer programproduct of claim 38 wherein the step of receiving an indication that asender desires to deliver a document to a next stage on a routing listfor the document comprises: receiving a parameter from the sender,wherein the recipient depends on the parameter received.
 40. Thecomputer program product of claim 29 wherein the step of receiving anindication that a sender desires to deliver a document to a next stageon a routing list for the document comprises: receiving the documenttogether with the indication.
 41. The computer program product of claim29 wherein the step of receiving an indication that a sender desires todeliver a document to a next stage on a routing list for the documentcomprises: receiving a form containing rules for the routing list. 42.The computer program product of claim 29 wherein the step of receivingan indication that a sender desires to deliver a document to a nextstage on a routing list for the document comprises: receiving a routingparameter for the routing list.
 43. The computer program product ofclaim 29 wherein the program code is further adapted to perform thesteps of: authenticating the sender using the sender's public key;establishing a first secure connection with the sender; and receivingthe document from the sender via the first secure connection.
 44. Thecomputer program product of claim 43 wherein the program code is furtheradapted to perform the steps of: authenticating the recipient using therecipient's public key; establishing a second secure connection with therecipient; and transmitting the document to the recipient via the secondsecure connection.
 45. An operations center for facilitating a securedelivery of a document from a sender to a next recipient on a routinglist, the operations center comprising: means for receiving anindication that a sender desires to deliver a document to a next stageon a routing list for the document; means for identifying a recipientfrom the next stage of the routing list; and means for generating anescrow encryption key; means for searching for a public key for therecipient, and if found, for encrypting the document using therecipient's public encryption key, wherein the recipient's public key isnot equal to said escrow encryption key; means for encrypting thedocument using the escrow encryption key if the means for searching doesnot return a public encryption key for the recipient; for requesting therecipient's public key from the recipient; for storing said document inescrow until receipt of the recipient's public key; for unencrypting thedocument using an escrow decryption key; and for re-encrypting thedocument using the recipient's encryption key prior to sending thedocument to the recipient, and means for providing the recipient'sencryption key encrypted document to the recipient.
 46. The operationscenter of claim 45 further comprising: means for sending the escrowencryption key to the sender.
 47. The operations center of claim 45wherein: the routing list is identified by an email address; and themeans for receiving an indication that a sender desires to deliver adocument to a next stage on the routing list includes means forreceiving the email address.
 48. The operations center of claim 45wherein: the routing list is identified by an address at a domain namefor routing lists; and the means for receiving an indication that asender desires to deliver a document to a next stage on the routing listincludes means for receiving the address.
 49. The operations center ofclaim 45 wherein the means for receiving an indication that a senderdesires to deliver a document to a next stage on the routing listcomprises: means for receiving a query from the sender for an identityof a recipient from the next stage of the routing list.
 50. Theoperations center of claim 45 further comprising: means for tracking acurrent recipient of the document from the routing list.
 51. Theoperations center of claim 45 wherein the routing list includes rules.52. The operations center of claim 45 wherein the routing list includesconditional recipients.
 53. The operations center of claim 45 whereinthe means for receiving an indication that a sender desires to deliver adocument to a next stage on a routing list for the document comprises:means for receiving the document together with the indication.
 54. Theoperations center of claim 45 wherein the means for receiving anindication that a sender desires to deliver a document to a next stageon a routing list for the document comprises: means for receiving a formcontaining rules for the routing list.
 55. The operations center ofclaim 45 wherein the means for receiving an indication that a senderdesires to deliver a document to a next stage on a routing list for thedocument comprises: means for receiving a routing parameter for therouting list.
 56. The operations center of claim 45 further comprising:means for authenticating the sender using the sender's public key; meansfor establishing a first secure connection with the sender; and meansfor receiving the document from the sender via the first secureconnection.
 57. The operations center of claim 56 further comprising:means for authenticating the recipient using the recipient's public key;means for establishing a second secure connection with the recipient;and means for transmitting the document to the recipient via the secondsecure connection.